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& \\
\multicolumn{2}{|c|}{\LARGE\bf THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 152 --- 21 June 2005 } & \multicolumn{1}{r|}{Editor: Bo Reipurth (reipurth@ifa.hawaii.edu)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
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%\vspace*{1cm}
%\begin{center}
%{\Large\em From the Editor}
%\end{center}
%\vspace*{0.6cm}
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\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.6cm}
{\large\bf{Orbits in Extended Mass Distributions:
General Results and the Spirographic Appoximation}}
%% Authors
{\bf{ Fred C. Adams$^{1}$ and Anthony M. Bloch$^{2}$}}
%% Institutions
$^1$ {Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109, USA} \\
$^2$ {Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, USA}
%% Email
{E-mail contact: fca@umich.edu}
%% LATEX COMMANDS
%% Abstract body
{This paper explores orbits in extended mass distributions and
develops an analytic approximation scheme based on epicycloids
(spirograph patterns). We focus on the Hernquist potential, which
provides a good model for many astrophysical systems, including
elliptical galaxies (with an $R^{1/4}$ law), dark matter halos (where
N-body simulations indicate a nearly universal density profile), and
young embedded star clusters (with gas density $\rho \sim
\xi^{-1}$). For a given potential, one can readily calculate orbital
solutions as a function of energy and angular momentum using numerical
methods. In contrast, this paper presents a number of analytic results
for the Hernquist potential and proves a series of general constraints
showing that orbits have similar properties for any extended mass
distribution. We discuss circular orbits, radial orbits, zero energy
orbits, different definitions of eccentricity, analogs of Kepler's
law, the definition of orbital elements, and the relation of these
orbits to spirograph patterns (epicycloids). Over a large portion of
parameter space, the orbits can be adequately described (with accuracy
better than 10\%) using the parametric equations of epicycloids,
thereby providing an analytic description of the orbits. As one
application of this formal development, we find a solution for the
orbit of the Large Magellanic Cloud in the potential of our Galaxy.
NOTE: For {\sl The Star Formation Newsletter}, the main applications
of these orbits are for forming star clusters.}
% Journal
{ Accepted by The Astrophysical Journal}
%% Preprints URL
astro-ph/0504661
\v5
%%--------SubmissionID=102----------------
%% Title
{\large\bf{H$_2$ Pure Rotational Lines in the Orion Bar}}
%% Authors
{\bf{ K. N. Allers$^{1}$, D. T. Jaffe$^{1}$, J. H. Lacy$^{1}$, B. T. Draine$^{2}$ and M. J. Richter$^{3}$}}
%% Institutions
$^1$ {Department of Astronomy, University of Texas at Austin, Austin, TX 78712-0259, USA} \\
$^2$ {Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA} \\
$^3$ {Department of Physics, University of California, Davis,1 Shields Avenue, Davis, CA 95616, USA}
%% Email
{E-mail contact: kallers@astro.as.utexas.edu}
%% LATEX COMMANDS
%% Abstract body
{Photodissociation regions, where UV radiation dominates the energetics and
chemistry of the neutral gas, contain most of the mass in the dense
interstellar medium of our galaxy. Observations of H$_2$ rotational and
ro-vibrational lines reveal that PDRs contain unexpectedly large amounts of
very warm (400-700 K) molecular gas. Theoretical models have difficulty explaining the existence of so much warm gas. Possible
problems include errors in the heating and cooling functions or in the
formation rate for H$_2$. To date, observations of H$_2$ rotational lines
smear out the structure of the PDR.
Only by resolving the hottest layers of H$_2$
can one test the predictions and assumptions of current models.
Using the Texas Echelon Cross Echelle Spectrograph (TEXES) we mapped
emission in the H$_2$
v = 0-0~S(1) and S(2) lines toward the Orion Bar PDR at 2"
resolution. We also observed H$_2$ v = 0-0~S(4) at selected points toward
the front of the PDR. Our maps cover a 12" by 40" region of
the bar where H$_2$ ro-vibrational lines are bright.
The distributions of H$_2$ 0-0~S(1), 0-0~S(2), and 1-0~S(1) line emission
agree in remarkable detail.
The high spatial resolution (0.002 pc) of our observations allows us
to probe the distribution of warm gas in the Orion Bar to a distance
approaching the scale length for FUV photon absorption. We use these
new observational results to set parameters for the PDR models
described in a companion paper (Draine et al. 2005, in prep). The
best-fit model can account for the separation of the H$_2$ emission
from the ionization front and the intensities of the ground state
rotational lines as well as the 1-0~S(1) and 2-1~S(1) lines. This
model requires significant adjustments to the commonly used values for
the dust UV attenuation cross section and the photoelectric heating
rate.}
% Journal
{ Accepted by ApJ}
%% Preprints URL
http://xxx.lanl.gov/abs/astro-ph/0506003
\v5
%%--------SubmissionID=93----------------
%% Title
{\large\bf{The Structure of Magnetocentrifugal Winds: I. Steady Mass Loading}}
%% Authors
{\bf{ Jeffrey M. Anderson$^{1}$, Zhi-Yun Li$^{1}$, Ruben Krasnopolsky$^{2}$ and Roger D. Blandford$^{3}$}}
%% Institutions
$^1$ {Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903, USA} \\
$^2$ {Center for Theoretical Astrophysics, University of Illinois at Urbana-Champaign, Loomis Laboratory, 1110 West Green Street, Urbana, IL 61801, USA} \\
$^3$ {SLAC, M/S 75, 2575 Sandhill Road, Menlo Park, CA 94025, USA}
%% Email
{E-mail contact: jma2u@virginia.edu}
%% LATEX COMMANDS
\newcommand{\solarmass}{{\,{\textnormal{M}}_\odot}}
\newcommand{\solarmassyear}{{\solarmass\yr^{-1}}}
\newcommand{\gauss}{\,{\textnormal{G}}}
\newcommand{\AU}{{\,\textnormal{AU}}}
\newcommand{\yr}{{\,\textnormal{yr}}}
%% Abstract body
{We present the results of a series of time-dependent numerical
simulations of cold, magnetocentrifugally launched winds from
accretion disks. The goal of this study is to determine how the mass
loading from the disk affects the structure and dynamics of the wind
for a given distribution of magnetic field. Our simulations span four
and half decades of mass loading; in the context of a disk with a
launching region from $0.1\AU$ to $1.0\AU$ around a $1\solarmass$ star
and a field strength of about $20\gauss$ at the inner disk edge, this
amounts to mass loss rates of $1\times 10^{-9}$ -- $3\times
10^{-5}\solarmassyear$ from each side of the disk. We find that, as
expected intuitively, the degree of collimation of the wind increases
with mass loading; however even the ``lightest'' wind simulated is
significantly collimated compared with the force-free magnetic
configuration of the same magnetic flux distribution at the launching
surface, which becomes radial at large distances. The implication is
that for flows from young stellar objects a radial field approximation
is inappropriate. Surprisingly, the terminal velocity of the wind and
the magnetic lever arm are still well-described by the analytical
solutions for a radial field geometry. We also find that the
isodensity contours and Alfv\'en surface are approximately
self-similar in mass loading. The wind becomes unsteady above some
critical mass loading rate. The exact value of the critical rate
depends on the (small) velocity with which we inject the material into
the wind. For a small enough injection speed, we are able to obtain
the first examples of a class of heavily-loaded magnetocentrifugal
winds with magnetic fields completely dominated by the toroidal
component all the way to the launching surface. The stability of such
toroidally dominated winds in 3D will be the subject of a future
investigation.}
% Journal
{ Accepted by ApJ}
%% Preprints URL
http://xxx.lanl.gov/abs/astro-ph/0410704
\v5
{\large\bf{Circumstellar Dust Disks in Taurus-Auriga: The
Submillimeter Perspective}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Sean M. Andrews$^1$ \ and Jonathan P. Williams$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {University of Hawaii Institute for Astronomy, Honolulu, HI 96822, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: andrews@ifa.hawaii.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present a sensitive, multiwavelength submillimeter continuum
survey of 153 young stellar objects in the Taurus-Auriga star
formation region. The submillimeter detection rate is 61\% to a
completeness limit of $\sim$10\,mJy (3-$\sigma$) at 850\,$\mu$m. The
inferred circumstellar disk masses are log-normally distributed with a
mean mass of $\sim 5 \times 10^{-3}$\,M$_{\odot}$ and a large
dispersion (0.5\,dex). Roughly one third of the submillimeter sources
have disk masses larger than the minimal nebula from which the solar
system formed. The median disk to star mass ratio is 0.5\%. The
empirical behavior of the submillimeter continuum is best described as
$F_{\nu} \propto \nu^{2.0 \pm 0.5}$ between 350\,$\mu$m and 1.3\,mm,
which we argue is due to the combined effects of the fraction of
optically thick emission and a flatter frequency behavior of the
opacity compared to the interstellar medium. This latter effect could
be due to a substantial population of large dust grains, which
presumably would have grown through collisional agglomeration. In
this sample, the only stellar property that is correlated with the
outer disk is the presence of a companion. We find evidence for
significant decreases in submillimeter flux densities, disk masses,
and submillimeter continuum slopes along the canonical infrared
spectral energy distribution evolution sequence for young stellar
objects. The fraction of objects detected in the submillimeter is
essentially identical to the fraction with excess near-infrared
emission, suggesting that dust in the inner and outer disk are removed
nearly simultaneously.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal }
%% If preprints are available on the WWW you can give the web
%% direction here.
preprint available on astro-ph/0506187
\v5
%%--------SubmissionID=92----------------
%% Title
{\large\bf{XMM-Newton spectroscopy of the metal depleted T Tauri star TWA 5}}
%% Authors
{\bf{ C. Argiroffi$^{1}$, A. Maggio$^{2}$, G. Peres$^{1}$, B. Stelzer$^{1,2}$ and R. Neuh\"auser$^{3}$}}
%% Institutions
$^1$ {Dipartimento di Scienze Fisiche ed Astronomiche, Sezione di Astronomia, Universit\`a di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy} \\
$^2$ {INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy} \\
$^3$ {Astrophysikalisches Institut und Universit\"ats-Sternwarte, Schillerg\"asschen 2-3, D-07745 Jena, Germany}
%% Email
{E-mail contact: argi@astropa.unipa.it}
%% LATEX COMMANDS
%% Abstract body
{We present results of X-ray spectroscopy for TWA~5, a member of the
young TW~Hydrae association, observed with {\it XMM-Newton}. TWA~5 is
a multiple system which shows H$\alpha$ emission, a signature typical
of classical T~Tauri stars, but no infrared excess. From the analysis
of the RGS and EPIC spectra, we have derived the emission measure
distribution vs. temperature of the X-ray emitting plasma, its
abundances, and the electron density. The characteristic temperature
and density of the plasma suggest a corona similar to that of
weak-line T~Tauri stars and active late-type main sequence
stars. TWA~5 also shows low iron abundance ($\sim 0.1$ times the solar
photospheric one) and a pattern of increasing abundances for elements
with increasing first ionization potential reminiscent of the inverse
FIP effect observed in highly active stars. The especially high ratio
${\rm Ne/Fe}\sim10$ is similar to that of the classical T~Tauri star
TW~Hya, where the accreting material has been held responsible for the
X-ray emission. We discuss the possible role of an accretion process
in this scenario. Since all T~Tauri stars in the TW Hydrae association
studied so far have very high ${\rm Ne/Fe}$ ratios, we also propose
that environmental conditions may cause this effect.}
% Journal
{ Accepted by Astronomy and Astrophysics}
%% Preprints URL
http://www.astropa.unipa.it/Library/preprint.html
\v5
{\large\bf{Magnetic field in Cepheus A as deduced from OH maser polarimetric
observations}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ A.~Bartkiewicz$^1$, M.~Szymczak$^1$, R.J.~Cohen$^2$ \ and
A.M.S.~Richards$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Toru\'n Centre for Astronomy, Nicolaus Copernicus University,
Gagarina 11, 87-100 Toru\'n, Poland} \\
$^2$ {Jodrell Bank Observatory, University of Manchester,
Macclesfield, Cheshire SK11 9DL, UK}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: annan@astro.uni.torun.pl}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present the results of MERLIN polarization mapping of OH masers at
1665 and 1667\,MHz towards the Cepheus\,A star-forming region. The
maser emission is spread over a region of 6 arcsec by 10 arcsec,
twice the extent previously detected. In contrast to the 22-GHz water
masers, the OH masers associated with H{\small II} regions show
neither clear velocity gradients nor regular structures. We
identified ten Zeeman pairs which imply a magnetic field strength
along the line-of-sight from $-$17.3 to $+$12.7\,mG. The magnetic
field is organised on the arcsecond scale, pointing towards us in the
west and away from us in the east side. The linearly polarized
components, detected for the first time, show regularities in the
polarization position angles depending on their position. The electric
vectors of OH masers observed towards the outer parts of H{\small II}
regions are consistent with the interstellar magnetic field
orientation, while those seen towards the centres of H{\small II}
regions are parallel to the radio-jets.
A Zeeman quartet inside a southern H{\small II} region has now been
monitored for 25 years; we confirm that the magnetic field decays
monotonically over that period.}
% Here you write which journal accepted your paper, for example:
{Accepted by MNRAS }
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprint available at http://arxiv.org/abs/astro-ph/0505374
\v5
%%--------SubmissionID=97----------------
%% Title
{\large\bf{VLT K-band spectroscopy of massive stars deeply embedded in IRAS sources with UCHII colours.}}
%% Authors
{\bf{ A. Bik$^{1,2}$, L. Kaper$^{2}$, M.M. Hanson$^{3}$ and M. Smits$^{2}$}}
%% Institutions
$^1$ {European Southern Observatory, Karl-Schwarzschild Strasse 2, Garching-bei-M\"unchen, D-85748, Germany} \\
$^2$ {Astronomical Institute ``Anton Pannekoek'', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam The Netherlands} \\
$^3$ {University of Cincinnati, Cincinnati, OH 45221-0011, U.S.A.}
%% Email
{E-mail contact: abik@eso.org}
%% LATEX COMMANDS
\newcommand{\kms}{km~s$^{-1}$}
\newcommand{\brg}{Br$\gamma$}
%% Abstract body
{We have obtained high resolution ($R$ = 10,000) $K$-band spectra of
candidate young massive stars deeply embedded in (ultra-) compact HII
regions (UCHIIs). These objects were selected from a near-infrared
survey of 44 fields centered on IRAS sources with UCHII
colours. Often, the near-infrared counterpart of the IRAS source is a
young embedded cluster hosting massive stars. In these clusters, three
types of objects are identified. The first type (38 objects) consists
of ``naked'' OB stars whose $K$-band spectra are dominated by
photospheric emission. We classify the $K$-band spectra of the OB-type
cluster members using near-infrared classification criteria. A few of
them have a very early (O3-O4~V) spectral type, consistent with a
young age of the embedded clusters. The spectral classification
provides an important constraint on the distance to the embedded
cluster. The ionising power of the population thus derived is
compared to the information obtained from the infrared and radio flux
of these sources. In most cases these two different determinations of
the ionising flux are consistent, from which we conclude that we have
identified the ionising star(s) in about 50 \% of the embedded
clusters. The second type (7 objects) are point sources associated
with UCHII radio emission, that exhibit nebular emission lines in the
near-infrared. Six of the objects in this group produce HeI emission
indicative of an embedded O-type star. These objects are more embedded
than the OB stars and probably do not dominate the infrared flux as
measured by IRAS. They may emit the bulk of their reprocessed UV
radiation at mm wavelengths. The third type (20 objects) is
characterised by broad (100--200~\kms) \brg\ emission and no
photospheric absorption profiles. In a forthcoming paper we show that
these objects are massive YSO candidates surrounded by dense
circumstellar disks.}
% Journal
{ Accepted by Astronomy and Astrophysics
%% Preprints URL
http://www.eso.org/$\sim$abik/publications.html (or astro-ph/0505293)}
\vspace{0.5cm}
{\large\bf{
Spitzer Observations of CO$_2$ Ice Towards Field Stars in the Taurus
Molecular Cloud
}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{
Edwin A. Bergin$^1$,
Gary J. Melnick$^2$,
Perry A. Gerakines$^3$,
David A. Neufeld$^4$,
Douglas C.B. Whittet$^5$
}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${University of Michigan, 825 Dennison Building, 500 Church Street.,
Ann Arbor, MI 48109-1090, USA} \\
$^2${Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138, USA}\\
$^3${Astro- and Solar-System Physics Program, Department of Physics, University
of Alabama at Birmingham, 1300 University Blvd, CH 310, Birmingham, AL
35294-1170, USA
}\\
$^{4}${Department of Physics and Astronomy, The Johns Hopkins University,
3400 North Charles Street, Baltimore, MD 21218, USA
}\\
$^{5}${Department of Physics, Applied Physics, and Astronomy, and New York Center
for Studies on the Origins of Life, Rensselaer Polytechnic Institute, Troy,
NY 12180, USA
}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: ebergin@umich.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{ We present the first {\em Spitzer} Infrared Spectrograph
observations of the 15.2 $\mu$m bending mode of CO$_2$ ice towards
field stars behind a quiescent dark cloud. CO$_2$ ice is detected
towards 2 field stars (Elias 16, Elias 3) and a single protostar (HL
Tau) with an abundance of $\sim 15-20\%$ relative to water ice.
CO$_2$ ice is not detected towards the source with lowest extinction
in our sample, Tamura~17 (A$_V$ = 3.9$^m$). A comparison of the Elias
16 spectrum with laboratory data demonstrates that the majority of
CO$_2$ ice is embedded in a polar H$_2$O-rich ice component, with
$\sim$15\% of CO$_2$ residing in an apolar H$_2$O-poor mantle. This is
the first detection of apolar CO$_2$ towards a field star. We find
that the CO$_2$ extinction threshold is A$_V = 4^m \pm 1^m$,
comparable to the threshold for water ice, but significantly less than
the threshold for CO ice, the likely precursor of CO$_2$. Our results
confirm CO$_2$ ice forms in tandem with H$_2$O ice along quiescent
lines of sight. This argues for CO$_2$ ice formation via a mechanism
similar to that responsible for H$_2$O ice formation, viz. simple
catalytic reactions on grain surfaces. }
{ Accepted by Astrophysical Journal {\it Letters}}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprint available at {\tt http://xxx.lanl.gov/abs/astro-ph/0505345}}
\v5
{\large\bf{Deuterated H$_3^+$ in proto-planetary disks}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Cecilia Ceccarelli$^1$ \& Carsten Dominik$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Laboratoire d'Astrophysique, Observatoire de Grenoble -
BP 53, F-38041 Grenoble cedex 09, France } \\
$^2$ {Sterrenkundig Instituut ``Anton Pannekoek'', Kruislaan 403, NL-1098SJ
Amsterdam, The Netherlands}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: Cecilia.Ceccarelli@obs.ujf-grenoble.fr}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{Probing the gas and dust in proto-planetary disks is central
for understanding the process of planet formation. In disks
surrounding solar type protostars, the bulk of the disk mass resides
in the outer midplane, which is cold ($\leq$20 K), dense ($\geq
10^7$ cm$^{-3}$) and depleted of CO. Observing the disk midplane
has proved, therefore, to be a formidable challenge. Ceccarelli et
al. (2004) detected H$_2$D$^+$ emission in a proto-planetary disk
and claimed that it probes the midplane gas. Indeed, since all
heavy-elements bearing molecules condense out onto the grain
mantles, the most abundant ions in the disk midplane are predicted
to be H$_3^+$ and its isotopomers. In this article, we carry out a
theoretical study of the chemical structure of the outer midplane of
proto-planetary disks. Using a self-consistent physical model for
the flaring disk structure, we compute the abundances of H$_3^+$ and
its deuterated forms across the disk midplane. We also provide the
average column densities across the disk of H$_3^+$, H$_2$D$^+$,
HD$_2^+$ and D$_3^+$, and line intensities of the ground transitions
of the ortho and para forms of H$_2$D$^+$ and HD$_2^+$
respectively. We discuss how the results depend on the cosmic ray
ionization rate, dust-to-gas ratio and average grain radius, and
general stellar/disk parameters. An important factor is the poorly
understood freeze-out of N$_2$ molecules onto grains, which we
investigate in depth. We finally summarize the diagnostic values of
observations of the H$_3^+$ isotopomers.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomy \& Astrophysics }
%% If preprints are available on the WWW you can give the web
%% direction here.
astro-ph/0506254
\v5
{\large\bf{Far-IR SEDs of Embedded Protostars and Dusty Galaxies: I. Theory for Spherical Sources}}
%% Authors
{\bf{ Sukanya Chakrabarti$^{1}$ and Christopher F. McKee$^{1}$}}
%% Institutions
$^1$ {University of CA, Berkeley, USA}
%% Email
{E-mail contact: sukanya@astro.berkeley.edu}
%% LATEX COMMANDS
%% Abstract body
{We present analytic radiative transfer solutions for the spectra of
unresolved, spherically symmetric, centrally heated, dusty sources.
We find that the dust thermal spectrum possesses scaling relations
that provide a natural classification for a broad range of sources,
from low-mass protostars to dusty galaxies. In particular, we find
that, given our assumptions, spectral energy distributions (SEDs) can
be characterized by two distance-independent parameters, the
luminosity-to-mass ratio, $L/M$, and the surface density, $\Sigma$,
for a set of two functions, namely, the density profile and the
opacity curve. The goal is to use SEDs as a diagnostic tool in
inferring the large-scale physical conditions in protostellar and
extragalactic sources, and ultimately, evolutionary parameters.
Our approach obviates the need to use SED templates in
the millimeter to far-infrared region of the spectrum; this is a
common practice in the extragalactic community that relies on observed
correlations established at low redshift that may not necessarily
extend to high redshift. Further, we demarcate the limited region of
parameter space in which density profiles can be inferred from the
SED, which is of particular import in the protostellar community as
competing theories of star formation are characterized by different
density profiles. The functionality of our model is unique in that in
provides for a self-consistent analytic solution that we have
validated by comparison with a well-tested radiative transfer code
(DUSTY) to
find excellent agreement with numerical results over a parameter space
that spans low-mass protostars to ultra-luminous infrared
galaxies (ULIRGS).}
% Journal
{ Accepted by Astrophysical Journal}
%% Preprints URL
\clearpage
{\large\bf{IRAS~16293$-$2422: proper motions, jet precession, the hot
core, and the unambiguous detection of infall}}
{\bf{Claire J. Chandler$^1$, Crystal L. Brogan$^2$, Yancy L.
Shirley$^1$, and Laurent Loinard$^3$}}
$^1$ {National Radio Astronomy Observatory, PO Box O, Socorro, NM
87801, USA}\\
$^2$ {University of Hawaii, Institute for Astronomy, 640 North
A'ohoku Place, Hilo, HI 96720, USA}\\
$^3$ {Centro de Radioastronom\'\i a y Astrof\'\i sica, Universidad
Nacional Aut\'onoma de M\'exico, \\ Apdo Postal 72--3 (Xangari), 58089
Morelia, Michoac\'an, M\'exico}
{E-mail contact: cchandle@nrao.edu}
{We present high spatial resolution observations of the multiple
protostellar system IRAS~16293$-$2422 using the Submillimeter Array
(SMA) at 300~GHz, and the Very Large Array (VLA) at frequencies from
1.5 to 43~GHz. This source was already known to be a binary system
with its main components, A and B, separated by $\sim 5''$. The new SMA
data now separate source A into two submillimeter continuum components,
which we denote Aa and Ab. The strongest of these, Aa, peaks between
the centimeter radio sources A1 and A2, but the resolution of the
current submillimeter data is insufficient to distinguish whether this
is a separate source or the centroid of submillimeter dust emission
associated with A1 and A2. Archival VLA data spanning 18 years show
proper motion of sources A and B of 17~mas~yr$^{-1}$, associated with the
motion of the $\rho$ Ophiuchi cloud. We also find, however, significant
relative motion between the centimeter sources A1 and A2 which excludes
the possibility that these two sources are gravitationally bound unless
A1 is in a highly eccentric orbit and is observed at periastron, the
probability of which is low. A2 remains stationary relative to source B,
and we identify it as the protostar which drives the large-scale NE--SW
CO outflow. A1 is shock-ionized gas which traces the location of the
interaction between a precessing jet and nearby dense gas. This jet
probably drives the large-scale E--W outflow, and indeed its motion
is consistent with the wide opening angle of this flow. The origin
of this jet must be located close to A2, and may be the submillimeter
continuum source Aa. Thus source A is now shown to comprise three
(proto)stellar components within $1''$. Source B, on the other hand,
is single, exhibits optically-thick dust emission even at 8~GHz, has a
high luminosity, and yet shows no sign of outflow. It is probably very
young, and may not even have begun a phase of mass loss yet.
The SMA spectrum of IRAS~16293$-$2422 reports the first astronomical
identification of many lines of organic and other molecules at 300 and
310~GHz. The species detected are typical of hot cores, the emission
from which is mainly associated with source A\@. The abundances of
second generation species, especially of sulphur-bearing molecules,
are significantly higher than predicted by chemical models for this
source to date, and we suggest that shocks are probably needed to explain
these enhancements. The peaks in the integrated emission from molecules
having high rotation temperatures coincide with the centimeter source
A1, also highlighting the key role of shocks in explaining the nature
of hot cores. Finally, we use the high brightness temperature of the
submillimeter dust emission from source B to demonstrate the unambiguous
detection of infall by observing redshifted SO ($7_7$$-$$6_6$) absorption
against the emission from its dust disk.}
{Accepted by ApJ}
{Preprint available at http://arxiv.org/abs/astro-ph/0506435}
\v5
{\large\bf{Variability of the NGC 1333 IRAS 4A Outflow:
Silicon Monoxide Observations}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Minho Choi$^1$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Taeduk Radio Astronomy Observatory,
Korea Astronomy and Space Science Institute,
Hwaam 61-1, Yuseong, Daejeon 305-348, Korea}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: minho@trao.re.kr}
%% Within the following brackets you place your text:
{ The NGC 1333 IRAS 4A region was observed in the SiO $v=0$
$J=1\rightarrow0$ line with an angular resolution of about 2$''$. The
SiO map revealed highly collimated outflows consisting of compact
emission peaks. The map shows at least two outflows: the main bipolar
outflow in the northeast-southwest direction and a shorter one toward
the south. The main outflow displays a sharp bend in the middle of
the northeastern lobe. The existence of a dense molecular cloud core
just north of the bend suggests that the outflow may have been
deflected as a result of jet-core collision. This explanation is also
supported by the asymmetric morphology of the bipolar outflow, the
good collimation and complicated kinematics of the deflected flow, the
low-velocity emission from the molecular gas near the bend, and the
enhancement of SiO emission in the deflected flow. The projected
deflection angle is about 34$^\circ$, and a significant fraction of
the kinetic energy of the outflow may have been transferred to the
ambient cloud through the collision process. Since the main outflow
is highly collimated, it was possible to identify the driving source.
The longer main outflow is probably driven by IRAS 4A2, the secondary
member of the protobinary system, and the shorter southern outflow by
A1, the primary. Possible explanations for this anti-correlation
between outflow and accretion include a delay of the onset of outflow
activity in A1 and a reversal of accretion rates between binary
components. }
% Here you write which journal accepted your paper, for example:
{Accepted by ApJ}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprint: {\verb+http://www.trao.re.kr/~minho/Publications.html+}}
\v5
{\large\bf{Is G84.0+0.8 a high mass star formation site near the edge of
the Pelican nebula?}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ F. Comer\'on$^1$, A. Pasquali$^2$ \ and J. Torra$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {European Southern Observatory, Karl-Schwarzschild-Strasse 2,
D-85748 Garching, Germany} \\
$^2$ {Institute of Astronomy, ETH Hoenggerberg, CH-8093 Zurich,
Switzerland} \\
$^3$ {Departament d'Astronomia i Meteorologia, Universitat de
Barcelona, E-08028 Barcelona, Spain}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: fcomeron@eso.org}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present visible and near-infrared observations of the
G84.0+0.8 HII region, a bright compact knot projected within the
boundaries of the W80 complex dominated by the North America and
Pelican nebulae. The spectrum of the nebula indicates a
temperature of the ionizing stellar spectrum $T_* \simeq 40,000 -
45,000$~K (corresponding to a O7-O5 star) and a density of the HII
region $n \simeq 460$~cm$^{-3}$, with a foreground extinction of
$A_V \simeq 5.9$~mag. A comparison of narrow-band near-infrared
images through the Br$\gamma$ and the H$_2$~$S(1)~v=1 \rightarrow
0$ filters shows that G84.0+0.8 consists of a fan-shaped cavity in
a molecular cloud at least partly bounded by a photodissociation
region, filled with Br$\gamma$-emitting ionized gas, and with a
compact cluster at the tip of the fan. The brightest star at the
position of the cluster is found to be a late G-type interloper.
While membership of G84.0+0.8 in the local arm is well established
from existing radial velocity measurements of the ionized gas, we
find that the ionizing flux estimated from the size and density of
the nebula on the one hand, and the radio continuum properties of
the nebula on the other hand, are well below the expected ionizing
flux of a mid, or even late, O-type star. We consider the
possibility that G84.0+0.8 might be externally ionized by a nearby
mid-O star. Currently available observations do not definitely
confirm or reject the membership of G84.0+0.8 in the W80 complex,
although a larger distance seems favored by the available data.
Nevertheless, we can firmly rule out the possibility that it
represents a massive star forming site in that complex, as its
appearance as a compact HII region containing an embedded cluster
may lead one to think.}
% Here you write which journal accepted your paper, for example:
{Accepted by Astronomy and Astrophysics}
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprints available from {\tt
http://www.eso.org/$\sim$fcomeron/g84.ps.gz}
\v5
{\large\bf{The Young Cluster NGC 2362}}
%% Authors
{\bf{ S. E. Dahm$^{1}$}}
%% Institutions
$^1$ {Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive,
Honolulu, HI 96822, USA}
%% Email
{E-mail contact: dahm@ifa.hawaii.edu}
%% LATEX COMMANDS
%% Abstract body
{An H$\alpha$ emission survey of the young cluster NGC 2362 resulted
in the detection of 130 H$\alpha$ emission stars in an
11$'$$\times$11$'$ field approximately centered upon the 4$^{th}$
magnitude O9Ib multiple star, $\tau$ CMa. The survey was carried out
using the wide-field grism spectrograph (WFGS) on the University of
Hawaii (UH) 2.2 meter telescope and the Gemini Multi-Object
Spectrograph (GMOS) on Gemini North. Deep optical $VR_{c}I_{c}$ (to
$V\sim23.0$) and near infrared (NIR) photometry ($JHK$) to $K\sim16$
were obtained for several fields within the cluster. Spectra covering
the 6000--8000\AA\ region at a resolution of R$\sim$3000 (adequate for
the determination of Li I $\lambda$6708 line strengths) were also
acquired for $\sim$200 PMS candidates with GMOS. Ages and masses for
the H$\alpha$ emitters in NGC 2362 were inferred from the isochrones
and evolutionary tracks of D'Antona \& Mazzitelli (DM97) as well as
Baraffe et al. (B98). An estimated cluster age of $\sim$1.8 Myr
follows from the models of DM97 and 3.5--5.0 Myr from those of
B98. The fraction of the T Tauri star (TTS) population that is
composed of weak-line emitters, $\it{f}$(WTTS), is 0.91, compared with
0.43 for the TTS population of NGC 2264. On the basis of W(H$\alpha$)
alone, the fraction of TTSs still undergoing accretion is 5--9\%,
comparable to the inner disk fraction determined from $JHKL-$band
excesses by Haisch, Lada, and Lada (12\%). Approximately 15\% of the
PMS sample in this study exhibits possible NIR excess, having
$E_{H-K}$ $>$0.1 mag. Given the lack of NIR excess and strong
H$\alpha$ emission from the majority of cluster members, it is
inferred that the inner disk regions of the TTS population have
dissipated significantly. The mean level of chromospheric activity
among the WTTS population of NGC 2362 is
log($L_{H\alpha}$/$L_{bol}$)$=-$3.65, significantly greater than that
of the low-mass population of the 600 Myr old Hyades cluster,
log($L_{H\alpha}$/$L_{bol}$)$=-$3.90. The total mass of the H$\alpha$
emitters and the OB stellar population of NGC 2362 define a lower
limit for the cluster mass of $\sim$300 M$_{\odot}$. Allowance for A
and F-type stars still on the radiative track, multiplicity, outlying
members, and the low-mass population lying below the completeness
limit of the H$\alpha$ emission survey increases this lower limit to
well over 500 M$_{\odot}$. The derived relaxation, disruption, and
evaporation timescales for the cluster imply that NGC 2362 will likely
survive beyond the age of the Pleiades, but statistics of galactic
cluster lifetimes favor its disruption well before the age of the
Hyades.}
% Journal
{ Accepted by Astronomical Journal}
%% Preprints URL
\v5
%%--------SubmissionID=94----------------
%% Title
{\large\bf{X-ray Diagnostics of Grain Depletion in Matter Accreting onto
T Tauri Stars}}
%% Authors
{\bf{ Jeremy J. Drake$^{1}$, Paola Testa$^{2}$ and Lee Hartmann$^{1}$}}
%% Institutions
$^1$ {Smithsonian Astrophysical Observatory, MS-3, 60 Garden Street, Cambridge, MA 02138, USA} \\
$^2$ {Kavli Institute for Astrophysics and Space Research, Massachusetts Institute for Technology, 70 Vassar Street, Cambridge, MA 02139, USA}
%% Email
{E-mail contact: jdrake@cfa.harvard.edu}
%% LATEX COMMANDS
%% Abstract body
{Recent analysis of high resolution {\it Chandra} X-ray spectra has
shown that the Ne/O abundance ratio is remarkably constant in stellar
coronae. Based on this result, we point out the utility of the Ne/O
ratio as a discriminant for accretion-related X-rays from T~Tauri
stars, and for probing the measure of grain-depletion of the accreting
material in the inner disk. We apply the Ne/O diagnostic to the
classical T~Tauri stars BP~Tau and TW~Hya---the two stars found to
date whose X-ray emission appears to originate, at least in part, from
accretion activity. We show that TW~Hya appears to be accreting
material which is significantly depleted in O relative to Ne. In
constrast, BP~Tau has an Ne/O abundance ratio consistent with that
observed for post-T~Tauri stars. We interpret this result in terms of
the different ages and evolutionary states of the circumstellar disks
of these stars. In the young BP~Tau disk (age $\sim 0.6$~Myr) dust is
still present near the disk corotation radius and can be ionized and
accreted, re-releasing elements depleted onto grains. In the more
evolved TW~Hya disk (age $\sim 10$~Myr), evidence points to ongoing
coagulation of grains into much larger bodies, and possibly planets,
that can resist the drag
of inward-migrating gas, and accreting gas is consequently depleted of
grain-forming elements.}
% Journal
{ Accepted by ApJ Letters}
%% Preprints URL
\v5
%%--------SubmissionID=96----------------
%% Title
{\large\bf{VLA 3.5 cm continuum sources in the Serpens cloud core}}
%% Authors
{\bf{ C. Eiroa$^{1}$, J.M Torrelles$^{2}$, S. Curiel$^{3}$ and A.A. Djupvik$^{4}$}}
%% Institutions
$^1$ {Dpto. F\'\i sica Te\'orica, C-XI, Facultad de Ciencias,
Universidad Aut\'onoma de Madrid, Cantoblanco, 28049 Madrid, Spain} \\
$^2$ {Instituto de Ciencias del Espacio (CSIC) and Institut d'Estudis
Espacials de Catalunya, C/ Gran Capit\'a 2-4, 08034 Barcelona, Spain} \\
$^3$ {Instituto de Astronom\'\i a, UNAM, Apdo. Postal 70-264, 04510 M\'exico
D.F., M\'exico and Harvard-Smithsonian Center for Astrophysics, 60 Garden St,
Cambridge, MA02138, USA} \\
$^4$ {Nordic Optical Telescope, Apdo. 474, 38700 Santa Cruz de La Palma}
%% Email
{E-mail contact: carlos.eiroa@uam.es}
%% LATEX COMMANDS
%% Abstract body
{We present VLA 3.5 cm continuum observations of the Serpens cloud core.
22 radio
continuum sources are detected. 16 out of the 22 cm sources are suggested to
be associated with young stellar objects (Class 0, Class I, flat-spectrum,
and Class II) of the young Serpens cluster. The rest of the VLA sources
plausibly are background objects. Most of the Serpens cm sources likely
represent thermal radio jets; on the other hand, the radio continuum emission
of some sources could be due to a gyrosynchroton mechanism arising from
coronally active young stars. The Serpens VLA sources are spatially
distributed into two groups; one of them located towards the NW clump of the
Serpens core, where only Class 0 and Class I protostars are found to present
cm emission, and a second group located towards the SE clump, where radio
continuum sources are associated with objects in evolutionary classes from
Class 0 to Class II. This subgrouping is similar to that found in the
near IR, mid-IR and mm wavelength regimes.}
% Journal
{ Accepted by Astronomical journal}
%% Preprints URL
http://arxiv.org/abs/astro-ph/0506054
\v5
{\large\bf{Mass loss at the lowest stellar masses}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ M. Fern\'andez$^{1,2}$ \ and F. Comer\'on$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl 17, D-69117
Heidelberg, Germany}\\
$^2$ {Instituto de Astrof\'{\i}sica de Andaluc\'{\i}a, CSIC, Camino Bajo
de
Hu\'etor 50, E-18008 Granada, Spain} \\
$^3$ {European Southern Observatory, Karl-Schwarzschild-Strasse 2,
D-85748 Garching, Germany}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: matilde@mpia-hd.mpg.de}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
We report the discovery of a jet in a [SII] image of Par-Lup3-4, a
remarkable M5-type pre-main sequence object in the Lupus 3
star-forming cloud. The spectrum of this star is dominated by the
emission lines commonly interpreted as tracers of accretion and
outflows. Par-Lup3-4 is therefore at the very low-mass end of the
exciting sources of jets. High resolution spectroscopy shows that the
[SII] line profile is double-peaked, implying that the low excitation
jet is seen at a small angle (probably $\geq$8$^{\circ}$) with respect
to the plane of the sky. The width of the H$_{\alpha}$ line suggests a
dominating contribution from the accretion columns and from the shocks
on the stellar surface. Unresolved H$_{\alpha}$ emission coming from
an object located at 4.2'' from Par-Lup3-4 is detected at a position
angle $\sim$30$^{\circ}$ or $\sim$210$^{\circ}$, with no counterpart
seen either in visible or infrared images.
We also confirm previous evidence of strong mass loss from the very
low mass star LS-RCrA~1, with spectral type M6.5 or later. All its
forbidden lines are blueshifted with respect to the local standard of
rest (LSR) of the molecular cloud at a position very close to the
object and the line profile of the [OI] lines is clearly
asymmetric. Thus, the receding jet could be hidden by a disk which is
not seen edge-on.
If an edge-on disk does not surround Par-Lup3-4 or LS-RCrA~1, an
alternative explanation, possibly based on the effects of mass
accretion, is required to account for their unusually low
luminosities. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomy \& Astrophysics }
%% If preprints are available on the WWW you can give the web
%% direction here.
%\begin{verbatim}
Preprint available at http://www.iaa.es/$\sim$matilde/jet\_vlms\_12.ps.gz
%\end{verbatim}
\v5
%%--------SubmissionID=103----------------
%% Title
{\large\bf{The effect of the Coriolis force on Kelvin-Helmholtz-driven mixing in protoplanetary disks.}}
%% Authors
{\bf{ Gilberto C. Gomez$^{1}$ and Eve C. Ostriker$^{1}$}}
%% Institutions
$^1$ {Astronomy Department, University of Maryland, College Park MD 20742, USA}
%% Email
{E-mail contact: gomez@astro.umd.edu}
%% LATEX COMMANDS
%% Abstract body
{We study the stability of proto-planetary disks with vertical
velocity gradients in their equilibrium rotation rates; such gradients
are expected to develop when dust settles into the midplane. Using a
linear stability analysis of a simple three-layer model, we show that
the onset of instability occurs at a larger value of the Richardson
number, and therefore for a thicker layer, when the ef\-fects of
Coriolis forces are included. This analysis also shows that
even-symmetry (midplane-crossing) modes develop faster than
odd-symmetry ones. These conclusions are corroborated by a large
number of nonlinear numerical simulations with two different
parameterized prescriptions for the initial (continuous) dust
distributions. Based on these numerical experiments, the Richardson
number required for marginal stability is more than an order of
magnitude larger than the traditional 1/4 value. The dominant modes
that grow have horizontal wavelengths of several initial dust scale
heights, and in nonlinear stages mix solids fairly homogeneously over
a comparable vertical range. We conclude that gravitational
instability may be more difficult to achieve than previously thought,
and that the vertical distribution of matter within the dust layer is
likely globally, rather than locally, determined.}
% Journal
{ Accepted by Astrophysical Journal}
%% Preprints URL
http://www.astro.umd.edu/~gomez/publica/khdisk.pdf
\v5
%%--------SubmissionID=104----------------
%% Title
{\large\bf{Limits on the primordial stellar multiplicity}}
%% Authors
{\bf{ Simon P Goodwin$^{1}$ and Pavel Kroupa$^{2}$}}
%% Institutions
$^1$ {School of Physics \& Astronomy, Cardiff University, 5 The Parade, Cardiff, CF24 3YB, UK} \\
$^2$ {Sternwarte, Universit\"at Bonn, Auf dem H\"ugel 71, D 53121, Bonn, Germany}
%% Email
{E-mail contact: Simon.Goodwin@astro.cf.ac.uk}
%% LATEX COMMANDS
%% Abstract body
{Most stars - especially young stars - are observed to be in multiple
systems. Dynamical evolution is unable to pair stars efficiently,
which leads to the conclusion that star-forming cores must usually
fragment into $\geq 2$ stars. However, the dynamical decay of systems
with $\geq 3$ or $4$ stars would result in a large single-star
population that is not seen in the young stellar population.
Additionally, ejections would produce a significant population of
close binaries that are not observed. This leads to a strong
constraint on star formation theories that cores must typically
produce only 2 or 3~stars. This conclusion is in sharp disagreement
with the results of currently available numerical simulations that
follow the fragmentation of molecular cores and typically predict the
formation of 5--10 seeds per core. In addition, open cluster remnants
may account for the majority of observed highly hierarchical
higher-order multiple systems in the field.}
% Journal
{ Accepted by A\&A}
%% Preprints URL
http://www.astro.cf.ac.uk/pub/Simon.Goodwin/2654.pdf
\v5
{\large\bf{Evidence for an X-Ray Jet in DG Tauri A?}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ M. G\"udel$^1$, S.~L. Skinner$^2$, K.~R. Briggs$^1$, M. Audard$^3$, K. Arzner$^1$,
\ and A. Telleschi$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Paul Scherrer Institut, W\"urenlingen and Villigen, CH-5232 Villigen PSI, Switzerland} \\
$^2$ {Center for Astrophysics and Space Astronomy, University of Colorado,
Boulder, CO 80309-0389, USA} \\
$^3$ {Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street,
New York, NY 10027, US}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: guedel@astro.phys.ethz.ch}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present evidence for an X-ray jet in the T Tau star DG Tau A based
on {\it Chandra} ACIS data. DG Tau A, a jet-driving classical T Tau
star with a flat infrared spectrum, reveals an unusual X-ray spectrum
that requires two thermal components with different intervening
absorption column densities. The softer component shows a low
temperature of $T \approx 2.9$~MK, and its absorption is compatible
with the stellar optical extinction (hydrogen column density $N_{\rm
H} \approx 5 \times 10^{21}$~cm$^{-2}$). In contrast, the harder
component reveals a temperature (22~MK) characteristic of active T Tau
stars but its emission is more strongly absorbed ($N_{\rm H} \approx
2.8 \times 10^{22}$~cm$^{-2}$). Furthermore, the high-resolution
ACIS-S image reveals a weak excess of soft ($0.5-2$~keV) counts at
distances of 2--4$^{\prime\prime}$ from the star precisely along the
optical jet, with a suggestive concentration at 4$^{\prime\prime}$
where a bow-shock-like structure has previously been identified in
optical line observations. The energy distribution of these photons is
similar to those of the stellar soft component. We interpret the soft
spectral component as originating from shocks at the base of the jet,
with shock heating continuing out to a distance of at least 500~AU
along the jet, whereas the hard component is most likely
coronal/magnetospheric as in other young stellar systems. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. (626, L53) }
%% If preprints are available on the WWW you can give the web
%% direction here.
WWW: http://www.astro.phys.ethz.ch/papers/guedel/guedel\_p\_nf.html
\v5
{\large\bf{Constraints on Inner Disk Evolution Timescales: A Disk Census of the eta Chamaeleontis Young Cluster}}
%% Authors
{\bf{ Karl E. Haisch Jr.$^{1}$, Ray Jayawardhana$^{2}$ and Jo\~ao Alves$^{3}$}}
%% Institutions
$^1$ {Physics Department, Utah Valley State College, Orem, UT 84058-5999, U.S.A.} \\
$^2$ {Department of Astronomy \& Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8, Canada} \\
$^3$ {European Southern Observatory, D-85748 Garching, Germany}
%% Email
{E-mail contact: Karl.Haisch@uvsc.edu}
%% LATEX COMMANDS
%% Abstract body
{We present new $L^\prime$-band (3.8$\mu$m) observations of stars in
the nearby ($\sim$97 pc) young ($\sim$6 Myr) compact cluster around
$\eta$ Chamaeleontis, obtained with the European Southern
Observatory's Very Large Telescope in Paranal, Chile. Our data,
combined with $J,H,K_{s}$ photometry from the 2-Micron All Sky Survey,
reveal that only two of the 12 members surveyed harbor $L^\prime$-band
excesses consistent with optically thick inner disks; both are also
likely accretors. Intriguingly, two other stars with possible evidence
for on-going accretion, albeit at very low rates, do not show
significant infrared excess: this may imply substantial grain growth
and/or partial clearing of the inner disk region, as expected in
planet formation scenarios. Our findings suggest that $\eta$ Cha stars
are in an epoch when disks are rapidly evolving, perhaps due to
processes related to planet building, and provide further constraints
on inner disk lifetimes.}
% Journal
{ Accepted by Astrophysical Journal Letters}
%% Preprints URL
http://arxiv.org/abs/astro-ph/0506352
\v5
%%--------SubmissionID=107----------------
%% Title
{\large\bf{The Disappearing Act of KH 15D: Photometric Results from 1995 to 2004}}
%% Authors
{ \bf{ Catrina M. Hamilton$^{1}$, William Herbst$^{2}$, Frederick
J. Vrba$^{3}$, Mansur A. Ibrahimov$^{4}$, Reinhard Mundt and Coryn
A. L. Bailer-Jones$^{5}$, Alexei V. Filippenko and Weidong Li$^{6}$,
Victor J.S. Bejar$^{7}$, Peter Abraham, Maria Kun, Attila Moor, Jozsef
Benko and Szilard Csizmadia$^{8}$ and Darren L. DePoy, Richard
W. Pogge, and Jennifer L. Marshall$^{9}$}}
%% Institutions
$^1$ {Mount Holyoke College, Astronomy Department, 50 College St., South Hadley, MA 01075, USA} \\
$^2$ {Astronomy Department, Wesleyan University, Middletown, CT 06459, USA} \\
$^3$ {US Naval Observatory, Flagstaff Station, Box 1149, Flagstaff, AZ, 86002-1149, USA} \\
$^4$ {Ulugh Beg Astronomical Institute of the Uzbek Academy of Sciences, Astronomicheskaya 33, 700052 Tashkent, Uzbekistan} \\
$^5$ {Max-Planck-Intitut fur Astronomie, Koniglstuhl 17, D-69117, Heidelberg, Germany} \\
$^6$ {Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA} \\
$^7$ {GTC Project. Instituto de Astrofisica de Canarias, IAC. E-38200. La Laguna, Tenerife, Spain} \\
$^8$ {Konkoly Observatory, H-1525, P.O. Box 67, Budapest, Hungary} \\
$^9$ {Department of Astronomy, Ohio State University, Columbus, OH 43210-1106, USA}
%% Email
{E-mail contact: chamilto@MtHolyoke.edu}
%% LATEX COMMANDS
%% Abstract body
{We present results from the most recent (2002--2004) observing
campaigns of the eclipsing system KH~15D, in addition to re-reduced
data obtained at Van Vleck Observatory (VVO) between 1995 and 2000.
Phasing nine years of photometric data shows substantial evolution in
the width and depth of the eclipses. The most recent data indicate
that the eclipses are now approximately 24 days in length, or half the
orbital period. These results are interpreted and discussed in the
context of the recent models for this system put forward by Winn et
al. (2004) and Chiang \& Murray-Clay (2004). A periodogram of the
entire data set yields a highly significant peak at 48.37 $\pm$ 0.01
days, which is in accord with the spectroscopic period of 48.38 $\pm$
0.01 days determined by Johnson et al. (2004). Another significant
peak, at 9.6 days, was found in the periodogram of the out-of-eclipse
data at two different epochs. We interpret this as the rotation
period of the visible star and argue that it may be tidally locked in
pseudosynchronism with its orbital motion. If so, application of
Hut's (1981) theory implies that the eccentricity of the orbit is $e$
= 0.65 $\pm$ 0.01. Analysis of the UVES/VLT spectra obtained by
Hamilton et al. (2003) shows that the $v\thinspace$sin$(i)$ of the
visible star in this system is 6.9 $\pm$ 0.3 km s$^{-1}$. Using this
value of $v\thinspace$sin$(i)$ and the measured rotation period of the
star, we calculate the lower limit on the radius to be $R = (1.3 \pm
0.1)\,$R$_{\odot}$, which concurs with the value obtained by Hamilton
et al. (2001) from its luminosity and effective temperature. Here we
assume that $i$ = 90$^o$ since it is likely that the spin and
orbital angular momenta vectors are nearly aligned. One unusually
bright data point obtained in the 1995/1996 observing season at VVO is
interpreted as the point in time when the currently hidden star (B)
made its last appearance. Based on this datum, we show that star B is
0.46 $\pm$ 0.03 mag brighter than the currently visible star A, which
is entirely consistent with the historical light curve (Johnson et
al. 2005). Finally, well-sampled $V_{J}$ and $I_{J}$ data obtained at
the CTIO/Yale 1-m telescope during 2001/2002 show an entirely new
feature: the system becomes bluer by a small but significant amount in
very steady fashion as it enters eclipse and shows an analogous
reddening as it emerges from eclipse. This suggests an extended zone
of hot gas located close to, but above, the photosphere of the
currently visible star. The persistance of the bluing of the light
curve shows that its length scale is comparable to a stellar radius.}
% Journal
{ Accepted by Astronomical Journal}
%% Preprints URL
\v5
%%--------SubmissionID=91----------------
%% Title
{\large\bf{IRAC Observations of Taurus Pre-Main Sequence Stars}}
%% Authors
{\bf{ Lee Hartmann$^{1}$, S.T. Megeath$^{1}$, Lori Allen$^{1}$, Kevin Luhman$^{1}$, Nuria Calvet$^{1}$, Paola D'Alessio$^{2}$, Ramiro Franco-Hernandez$^{2}$ and Giovanni Fazio$^{1}$}}
%% Institutions
$^1$ {Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA} \\
$^2$ {Centro de Radioastronomia y Astrofisica, Ap. P. 72-3 (Xangari) 58089 Morelia, Michoacan, Mexico}
%% Email
{E-mail contact: hartmann@cfa.harvard.edu}
%% LATEX COMMANDS
%% Abstract body
{We present infrared photometry obtained with the IRAC camera on the
{\em Spitzer} Space Telescope of a sample of 82 pre-main sequence
stars and brown dwarfs in the Taurus star-forming region. We find a
clear separation in some IRAC color-color diagrams between objects
with and without disks. A few ``transition'' objects are noted, which
correspond to systems in which the inner disk has been evacuated of
small dust. Separating pure disk systems from objects with remnant
protostellar envelopes is more difficult at IRAC wavelengths,
especially for objects with infall at low rates and large angular
momenta. Our results generally confirm the IRAC color classification
scheme used in previous papers by Allen et al. and Megeath et al. to
distinguish between protostars, T Tauri stars with disks, and young
stars without (inner) disks. The observed IRAC colors are in good
agreement with recent improved disk models, and in general accord with
models for protostellar envelopes derived from analyzing a larger
wavelength region. We also comment on a few Taurus objects of special
interest. Our results should be useful for interpreting IRAC results
in other, less well-studied star-forming regions.}
% Journal
{ Accepted by Astrophysical Journal}
%% Preprints URL
http://cfa-www.harvard.edu/cfa/youngstars/publications.html
\v5
{\large\bf{X-ray Emission from the Weak-lined T Tauri Binary System KH~15D}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ William Herbst$^1$ \ and Edward C. Moran$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Astronomy Department, Wesleyan University, Middletown, CT
06459, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: wherbst@wesleyan.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{The unique eclipsing, weak-lined T Tauri star KH~15D has been detected as an
X-ray source in a 95.7 ks exposure from the {\it Chandra X-ray Observatory\/}
archives. A maximum X-ray luminosity of $1.5 \times 10^{29}$ erg~s$^{-1}$ is
derived in the 0.5--8 keV band, corresponding to $L_{\rm X}/L_{\rm bol} =
7.5 \times 10^{-5}$. Comparison with samples of stars of similar effective
temperature in NGC 2264 and in the Orion Nebula Cluster shows that this is
about an order of magnitude low for a typical star of its mass and age. We
argue that the relatively low luminosity cannot be attributed to absorption
along the line of sight but implies a real deficiency in X-ray production.
Possible causes for this are considered in the context of a recently proposed
eccentric binary model for KH 15D. In particular, we note that the visible component rotates rather slowly for a weak-lined T Tauri star and has possibly been pseudosynchronized by tidal interaction with the primary near periastron.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
Available at: astro-ph/0506167
\v5
{\large\bf{Velocity field and star formation in the Horsehead nebula}}
%% Authors
{\bf{ P. Hily-Blant$^{1}$, D. Teyssier$^{2,3}$, S. Philipp$^{4}$ and R. Guesten$^{4}$}}
%% Institutions
$^1$ {Institut de Radio Astronomie Millimetrique (IRAM), France} \\
$^2$ {Space Research Organization, Netherlands} \\
$^3$ {Departamento de Astrofisica Molecular e Infrarroja, Spain} \\
$^4$ {Max-Planck-Institut fur Radioastronomie, Germany}
%% Email
{E-mail contact: hilyblan@iram.fr}
%% LATEX COMMANDS
\def \kmspc{\ensuremath{{\rm km\, s^{-1}\,pc^{-1}}}}
\def \kms{\ensuremath{{\rm km\, s^{-1}}}}
\def \pc{\ensuremath{{\rm pc}}}
\def \cdo {\ensuremath {{\rm C^{18}O}}}
\def \jone {\ensuremath{(1-0)}}
\def \jtwo {\ensuremath{(2-1)}}
%% Abstract body
{Using large scale maps in \cdo\jtwo\ and in the continuum at 1.2mm
obtained at the IRAM-30m antenna with the Heterodyne Receiver Array
(HERA) and MAMBO2, we investigated the morphology and the velocity
field probed in the inner layers of the Horsehead nebula. The data
reveal a non--self-gravitating ($m/m_{\rm vir}\approx 0.3$) filament
of dust and gas (the ``neck'', diametre = $0.15-0.30\,\pc$) connecting
the Horsehead western ridge, a Photon-Dominated Region illuminated by
$\sigma$Ori, to its parental cloud L1630. Several dense cores are
embedded in the ridge and the neck. One of these cores appears
particularly peaked in the 1.2\,mm continuum map and corresponds to a
feature seen in absorption on ISO maps around 7\,$\mu$m. Its \cdo\
emission drops at the continuum peak, suggestive of molecular
depletion onto cold grains. The channel maps of the Horsehead exhibit
an overall north-east velocity gradient whose orientation swivels
east-west, showing a somewhat more complex structure than was recently
reported by Pound et al 2003 using BIMA CO\jone\ mapping. In both the
neck and the western ridge, the material is rotating around an axis
extending from the PDR to L1630 (angular velocity
$=1.5-4.0\,\kms$). Moreover, velocity gradients along the filament
appear to change sign regularly (3\,\kmspc, period=0.30\,pc) at the
locations of embedded integrated intensity peaks. The nodes of this
oscillation are at the same velocity. Similar transverse cuts across
the filament show a sharp variation of the angular velocity in the
area of the main dense core. The data also suggest that differential
rotation is occurring in parts of the filament. We present a new
scenario for the formation and evolution of the nebula and discuss
dense core formation inside the filament.}
% Journal
{ Accepted by A\&A}
%% Preprints URL
\v5
{\large\bf{Grain Evolution across the Shocks in the L1448--mm Outflow}}
%% Authors
{\bf{ I. Jim\'enez--Serra$^{1}$, J. Mart\'{\i}n--Pintado$^{1}$, A. Rodr\'{\i}guez--Franco$^{1,2}$ and S. Mart\'{\i}n$^{3}$}}
%% Institutions
$^1$ {Dpto. de Astrof\'{\i}sica Molecular e Infrarroja (IEM-CSIC), C/ Serrano 121, 28006 Madrid, Spain} \\
$^2$ {Escuela Universitaria de \'Optica (UCM), Avda. Arcos de Jal\'on s/n, E--28037 Madrid, Spain} \\
$^3$ {IRAM, Avda. Divina Pastora, Local 20, E--18012 Granada, Spain}
%% Email
{E-mail contact: izaskun@damir.iem.csic.es}
%% LATEX COMMANDS
%% Abstract body
{The recent detection of the shock--precursors toward the very young
L1448--mm outflow offers the possibility to study the grain chemistry
during the first stages of the shock evolution, constraining the
molecules ejected from grains and the species formed in gas phase.
Observations of key molecules in the grain chemistry
like SiO, CH$_3$OH, SO, CS, H$_2$S, OCS, and SO$_2$ toward this
outflow are presented. The line
profiles and the derived abundances show three distinct velocity
regimes that trace the shock evolution: the preshock, the
shock--precursor and the postshock gas. The SiO, CH$_3$OH, SO, and CS
abundances are enhanced with respect to the quiescent gas
by one order of magnitude in the shock--precursor component,
and by three orders of magnitude in the postshock gas.
The derived SiO and CH$_3$OH abundances are
consistent with the recent ejection of these molecules from grains.
Since H$_2$S is only enhanced in the shock--precursor component, and
OCS and SO$_2$ are undetected, SO and
CS are the most abundant sulfur--bearing species in the grain
mantles of L1448--mm. The ejection of mainly SO and CS rather than
H$_2$S or OCS from grains, suggests that the sulfur chemistry will depend on
the chemical ``history'' of the grain mantles in outflows and hot
cores.}
% Journal
{ Accepted by Astrophysical Journal Letters}
%% Preprints URL
http://arxiv.org/abs/astro-ph/0506408
\v5
{\large\bf{Formation and Evolution of Planetary Systems: \\
Cold Outer Disks Associated with Sun-like stars
}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{
Jinyoung Serena Kim$^1$,
Dean C. Hines$^2$,
Dana E. Backman$^3$,
Lynne A. Hillenbrand$^4$,
Michael R. Meyer$^1$,
Jens Rodmann$^5$,
Amaya Moro-Mart{\'i}n$^6$,
John M. Carpenter$^4$,
Murray D. Silverstone$^1$,
Jeroen Bouwman$^5$,
Eric E. Mamajek$^7$,
Sebastian Wolf$^4$,
Renu Malhotra$^8$,
Ilaria Pascucci$^1$,
Joan Najita$^9$,
Deborah L. Padgett$^{10}$,
Thomas Henning$^5$,
Timothy Y. Brooke$^4$,
Martin Cohen$^{11}$,
Stephen E. Strom$^9$,
Elizabeth B. Stobie$^1$,
Charles W. Engelbracht$^1$, Karl D. Gordon$^1$,
Karl Misselt$^1$, Jane E. Morrison$^1$,
James Muzerolle$^1$, \& Kate Y. L. Su$^1$
}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ Steward Observatory, The University of Arizona, 933 N. Cherry Ave.,Tucson, AZ 85721-0065, USA \\
$^2$ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO \\
$^3$ SOFIA, MS 211-3, NASA-Ames, Moffet Field, CA 94035-1000, USA \\
$^4$ Astronomy, California Institute of Technology, Pasadena, CA 91125, USA \\
$^5$ Max-Planck-Institut fur Astronomie, D-69117, Heidelberg, Germany \\
$^6$ Princeton University, Princeton, NJ 08540, USA \\
$^7$ Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,MS-42 Cambridge, MA 02138, USA \\
$^8$ Department of Planetary Sciences \& Lunar and Planetary Laboratory,
The University of Arizona, 1629 E. University Blvd., Tucson, AZ85721-0092, USA \\
$^9$ National Optical Astronomy Observatory, 950 N. Cherry Ave.,Tucson, AZ 85719, USA \\
$^{10}$ Spitzer Science Center, California Institute of Technology, Pasadena, CA, 91125, USA \\
$^{11}$ Radio Astronomy, University of California, Berkeley, CA 94720, USA
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: serena@as.arizona.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
We present the discovery of debris systems around three solar mass stars
based upon observations performed with the {\it Spitzer Space Telescope}
as part of a Legacy Science Program, ``the Formation and Evolution
of Planetary Systems'' (FEPS). We also confirm the presence of debris
around two other stars. All the stars exhibit infrared emission in excess
of the expected photospheres in the 70~$\mu$m band, but are consistent with
photospheric emission at $\leq$33$~\mu$m. This restricts the maximum
temperature of debris in equilibrium with the stellar radiation to
$T < 70$~K. We find that these sources are relatively old in the FEPS
sample, in the age range 0.7 $-$ 3 Gyr. Based on models of the spectral
energy distributions, we suggest that these debris systems represent
materials generated by collisions of planetesimal belts.
We speculate on the nature of these systems through comparisons to our own
Kuiper Belt, and on the likely planet(s) responsible for
stirring the system and ultimately releasing dust through collisions.
We further report observations of a nearby star HD~13974 ($d =$ 11~pc) that
is indistinguishable from a bare photosphere at both 24~$~\mu$m and 70~$~\mu$m.
The observations place strong upper limits on the presence of any
cold dust in this nearby system ($L_{\rm IR}/L_\star < $10$^{-5.2}$).
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal }
%% If preprints are available on the WWW you can give the web
%% direction here.
{http://globule.as.arizona.edu/$\sim$serena/publications/JSK\_cold\_disks.ps}
\v5
{\large\bf{Photon dominated regions in the spiral arms of M83 and M51}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ C.\,Kramer$^1$, B.\,Mookerjea$^1$, E.\,Bayet$^2$,
S.\,Garcia-Burillo$^3$, M.\,Gerin$^2$, F.P.\,Israel$^4$, J.\,Stutzki$^1$,
and \\ J.G.A.\,Wouterloot$^5$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {KOSMA, I. Physikalisches Institut,
Universit\"at zu K\"oln,
Z\"ulpicher Stra\ss{}e 77,
50937 K\"oln, Germany} \\
$^2$ {Radioastronomie Millimetrique: UMR 8540 du CNRS,
Laboratoire de Physique de l'ENS, 24 Rue Lhomond,
75231 Paris cedex 05, France} \\
$^3$ {Centro Astronomico de Yebes,
IGN, E-19080 Guadalajara, Spain} \\
$^4$ {Sterrewacht Leiden,
P.O. Box 9513,
2300 RA Leiden, The Netherlands} \\
$^5$ {Joint Astronomy Centre,
660 N. A'ohoku Place, Hilo, HI, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: kramer@ph1.uni-koeln.de}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\TO}[0]{{-}}
\newcommand{\RM}[1]{\mathrm{#1}}
\newcommand{\NOTE}[1]{^{\mathrm{{\it #1}}}}
\newcommand{\kkms}[0]{\RM{K}\,\RM{km}\,\RM{s}^{-1}}
%\newcommand{\kms}[0]{\,\RM{km}\,\RM{s}^{-1}}
\newcommand{\micron}{\mbox{$\mu$m}}
\def\thCO{$^{13}$CO}
\def\twCO{$^{12}$CO}
\def\percc {$\hbox{{\rm cm}}^{-3}$}
\newcommand{\CIIw}{{C}{II}}
\newcommand{\CII}{[{C}{II}]}
\newcommand{\CIw}{{C}{I}}
\newcommand{\CI}{[{C}{I}]}
\newcommand{\OIw}{{O}{I}}
\newcommand{\OI}{[{O}{I}]}
\newcommand{\OIIIw}{{O}{III}}
\newcommand{\OIII}{[{O}{III}]}
\newcommand{\NIIIw}{{N}{III}}
\newcommand{\NIII}{[{N}{III}]}
%
\newcommand{\HII}{{H}{II}}
\newcommand{\HI}{{H}{I}}
\newcommand{\NIIw}{{N}{II}}
\newcommand{\NII}{[{N}{II}]}
\newcommand{\lsun}{L$_{\odot}$}
\newcommand{\msun}{M$_{\odot}$}
\newcommand{\msol}{M$_{\odot}$}
%\newcommand{\msun}{M$_{\rm sun}$}
%\newcommand{\msol}{M$_{\sun}$}
\newcommand{\cmcub}{cm$^{-3}$}
\newcommand{\cmsq}{cm$^{-2}$}
%% Within the following brackets you place your text:
{We present \CI\ $^3$P$_1$--$^3$P$_0$ spectra at four spiral arm
positions and the nuclei of the nearby galaxies M83 and M51 obtained
at the JCMT. The spiral arm positions lie at galacto-centric distances
of between 2\,kpc and 6\,kpc. This data is complemented with maps of
CO 1--0, 2--1, and 3--2, and ISO/LWS far-infrared data of \CII\
(158\,$\mu$m), \OI\ (63\,$\mu$m), and \NII\ (122\,$\mu$m) allowing for
the investigation of a complete set of all major gas cooling
lines. From the intensity of the \NII\ line, we estimate that between
15\% and $30$\% of the observed \CII\ emission originate from the
dense ionized phase of the ISM. The analysis indicates that emission
from the diffuse ionized medium is negligible. In combination with
the FIR dust continuum, we find gas heating efficiencies below
$\sim0.21\%$ in the nuclei, and between 0.25 and 0.36\% at the outer
positions. Comparison with models of photon-dominated regions (PDRs)
of Kaufman et al. (1999) with the standard ratios \OI(63)/\CII$_{\rm
PDR}$ and (OI(63)$+$\CII$_{\rm PDR}$) vs. TIR, the total infrared
intensity, yields two solutions. The physically most plausible
solution exhibits slightly lower densities and higher FUV fields than
found when using a full set of line ratios, \CII$_{\rm
PDR}$/\CI(1--0), \CI(1--0)/CO(3--2), CO(3--2)/CO(1--0), \CII/CO(3--2),
and, \OI(63)/\CII$_{\rm PDR}$. The best fits to the latter ratios
yield densities of $10^4$\,cm$^{-3}$ and FUV fields of
$\sim\,G_0=$20--30 times the average interstellar field without much
variation. At the outer positions, the observed total infrared
intensities are in perfect agreement with the derived best fitting FUV
intensities. The ratio of the two intensities lies at 4--5 at the
nuclei, indicating the presence of other mechanisms heating the dust.
\CI\ area filling factors lie below 2\% at all positions, consistent
with low volume filling factors of the emitting gas. The fit of the
model to the line ratios improves significantly if we assume that \CI\
stems from a larger region than CO 2--1. Improved modelling would need
to address the filling factors of the various submm and FIR tracers,
taking into consideration the presence of density gradients of the
emitting gas by including cloud mass and size distributions within the
beam.}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://www.ph1.uni-koeln.de/$\sim$kramer/
\v5
%%--------SubmissionID=101----------------
%% Title
{\large\bf{Comparisons of an Evolutionary Chemical Model with Other Models}}
%% Authors
{\bf{ Jeong-Eun Lee$^{1}$, Neal J. Evans II$^{1}$ and Edwin A. Bergin$^{2}$}}
%% Institutions
$^1$ {Department of Astronomy, The University of Texas at Austin, 1 University Station C1400, Austin, Texas 78712--0259} \\
$^2$ {Department of Astronomy, The University of Michigan, 825 Dennison Building Ann Arbor, Michigan 48109-1090}
%% Email
{E-mail contact: jelee@astro.as.utexas.edu}
%% LATEX COMMANDS
%% Abstract body
{We compare an evolutionary chemical model with simple empirical models
of the abundance and with static chemical models. We focus on
the prediction of molecular line profiles that are
commonly observed in low mass star forming cores. We show that
empirical models can be used to constrain evaporation radii and infall
radii using lines of some species. Species with more complex abundance
profiles are not well represented by the empirical models. Static
chemical models produce abundance profiles different from those obtained from
an evolutionary calculation because static models do not
account for the flow of matter inward from the outer regions.
The resulting profiles of lines used to probe infall may differ substantially.}
% Journal
{ Accepted by ApJ}
%% Preprints URL
http://arxiv.org/abs/astro-ph/0506086
\v5
{\large\bf{Collapse and Fragmentation of Rotating Magnetized Clouds. I.
Magnetic Flux - Spin Relation}}
%% Authors
{\bf{ Masahiro N Machida$^{1}$, Tomoaki Matsumoto$^{2}$, Kohji Tomisaka$^{3}$ and Tomoyuki Hanawa$^{4}$}}
%% Institutions
$^1$ {Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan} \\
$^2$ {Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan} \\
$^3$ {National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan} \\
$^4$ {Center for Frontier Science, Chiba University, Yayoicho 1-33, Inageku, Chiba 263-8522, Japan}
%% Email
{E-mail contact: machidam@scphys.kyoto-u.ac.jp}
%% LATEX COMMANDS
\newcommand{\cm }{\,{\rm cm}^{-3} }
%% Abstract body
{We discuss evolution of the magnetic flux density and angular
velocity in a molecular cloud core, on the basis of three-dimensional
numerical simulations, in which a rotating magnetized cloud fragments
and collapses to form a very dense optically thick core of $ > 5
\times 10 ^{10} \cm $. As the density increases towards the formation
of the optically thick core, the magnetic flux density and angular
velocity converge towards a single relationship between the two
quantities. If the core is magnetically dominated its magnetic flux
density approaches $1.5 (n/ 5 \times 10^{10} \, \cm )^{1/2}$~mG, while
if the core is rotationally dominated the angular velocity approaches
$2.57 \times 10^{-3} \, (n/5 \times 10^{10} \, \cm )^{1/2}$ yr$^{-1}$,
where $n$ is the density of the gas. We also find that the ratio of
the angular velocity to the magnetic flux density remains nearly
constant until the density exceeds $ 5 \times 10 ^{10} \cm $.
Fragmentation of the very dense core and emergence of outflows from
fragments are shown in the subsequent paper.}
% Journal
{ Accepted by MNRAS}
%% Preprints URL
astro-ph/0506439
\v5
{\large\bf{Collapse and Fragmentation of Rotating Magnetized Clouds. II.
Binary Formation and Fragmentation of First Cores}}
%% Authors
{\bf{ Masahiro N Machida$^{1}$, Tomoaki Matsumoto$^{2}$, Tomoyuki Hanawa$^{3}$ and Kohji Tomisaka$^{4}$}}
%% Institutions
$^1$ {Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan} \\
$^2$ {Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan} \\
$^3$ {Center for Frontier Science, Chiba University, Yayoicho 1-33, Inageku, Chiba 263-8522, Japan} \\
$^4$ {National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan}
%% Email
{E-mail contact: machidam@scphys.kyoto-u.ac.jp}
%% LATEX COMMANDS
%\newcommand{\cm }{\,{\rm cm}^{-3} }
%% Abstract body
{Subsequent to Paper I, the evolution and fragmentation of a rotating
magnetized cloud are studied with use of three-dimensional MHD
nested-grid simulations. After the isothermal runaway collapse, an
adiabatic gas forms a protostellar first core at the center of the
cloud. When the isothermal gas is stable for fragmentation in a
contracting disk, the adiabatic core often breaks into several
fragments. Conditions for fragmentation and binary formation are
studied. All the cores which show fragmentations are geometrically
thin, as the diameter-to-thickness ratio is larger than 3. Two
patterns of fragmentation are found. (1) When a thin disk is
supported by centrifugal force, the disk fragments through a ring
configuration (ring fragmentation). This is realized in a fast
rotating adiabatic core as $\Omega >0.2 \tau_{\rm ff}^{-1}$, where
$\Omega$ and $\tau_{\rm ff}$ represent the angular otation speed and
the free-fall time of the core, respectively. (2) On the other hand,
the disk is deformed to an elongated bar in the isothermal stage for a
strongly magnetized or rapidly rotating cloud. The bar breaks into 2 -
4 fragments (bar fragmentation). Even if a disk is thin, the disk
dominated by the magnetic force or thermal pressure is stable and
forms a single compact body. In either ring or bar fragmentation
mode, the fragments contract and a pair of outflows are ejected from
the vicinities of the compact cores. The orbital angular momentum is
larger than the spin angular momentum in the ring fragmentation. On
the other hand, fragments often quickly merge in the bar
fragmentation, since the orbital angular momentum is smaller than the
spin angular momentum in this case. Comparison with observations is
also shown.}
% Journal
{ Accepted by MNRAS}
%% Preprints URL
astro-ph/0506440
\v5
{\large\bf{Evaporation and condensation of HI clouds in thermally
bistable interstellar media: semi-analytic description of isobaric
dynamics of curved interfaces}}
%% Authors
{\bf{ Masahiro Nagashima$^{1}$, Hiroshi Koyama$^{2}$ and Shu-ichiro Inutsuka$^{1}$}}
%% Institutions
$^1$ {Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan} \\
$^2$ {Department of Earth and Planetary Science, Kobe University, Kobe 657-8501, Japan}
%% Email
{E-mail contact: masa@scphys.kyoto-u.ac.jp}
%% LATEX COMMANDS
%% Abstract body
{We analyse the evaporation and condensation of spherical and
cylindrical HI clouds of the cold neutral medium surrounded by the
warm neutral medium. Because the interstellar medium including those
two phases is well described as a thermally bistable fluid, it is
useful to apply pattern formation theories to the dynamics of the
interface between the two phases. Assuming isobaric evolution of
fluids and a simple polynomial form of the heat-loss function, we show
the curvature effects of the interface. We find that approximate
solutions for spherical clouds are in good agreement with numerically
obtained solutions. We extend our analysis to general curved
interfaces taking into account the curvature effects explicitly. We
find that the curvature effects always stabilize curved interfaces
under assumptions such as isobaric evolution we adopt in this Letter.}
% Journal
{ Accepted by MNRAS Letters}
%% Preprints URL
http://arxiv.org/abs/astro-ph/0503137
\v5
%%--------SubmissionID=100----------------
%% Title
{\large\bf{Quiescent Cores and the Efficiency of Turbulence-Accelerated,
Magnetically Regulated Star Formation}}
%% Authors
{\bf{ Fumitaka Nakamura$^{1}$ and Zhi-Yun Li$^{2}$}}
%% Institutions
$^1$ {Faculty of Education and Human Sciences, Niigata University, 8050 Ikarashi-2, Niigata 950-2181, Japan} \\
$^2$ {Astronomy Department, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903, USA}
%% Email
{E-mail contact: fnakamur@ed.niigata-u.ac.jp}
%% LATEX COMMANDS
%% Abstract body
{The efficiency of star formation, defined as the ratio of the stellar
to total (gas and stellar) mass, is observed to vary from a few
percent in regions of dispersed star formation to about a third in
cluster-forming cores. This difference may reflect the relative
importance of magnetic fields and turbulence in controlling star
formation. We investigate the interplay between (decaying) turbulence
and magnetic fields using numerical simulations, in a sheet-like
geometry. The geometry allows for an accurate and expedient
treatment of ambipolar diffusion, a key ingredient for star
formation. We demonstrate that star formation with an efficiency
of a few percent can occur over several gravitational collapse
times in moderately magnetically subcritical clouds that are
supersonically turbulent. In turbulent clouds that are marginally
magnetically supercritical, the star formation efficiency is higher,
but can still be consistent with the values inferred for nearby
embedded clusters. A phenomenological prescription for protostellar
outflow is included in our model to stop mass accretion after a
star has obtained a given mass and to disperse away the remaining
core material. Within a reasonable range of strength, the outflow
does not affect the efficiency of star formation much and contributes
little to turbulence replenishment in subcritical and marginally
supercritical clouds. If not regulated by magnetic fields at all,
star formation in a multi-Jeans mass cloud endowed with a strong
initial turbulence proceeds rapidly, with the majority of cloud mass
converted into stars in a gravitational collapse time in the absence
of constant turbulence driving. The efficiency is formally higher
than the values inferred for nearby cluster-forming cores, indicating
that magnetic fields are dynamically important even for cluster
formation.
In turbulent, magnetically subcritical clouds, the turbulence accelerates
star formation by reducing the time for dense core formation. The dense
cores produced in such clouds are predominantly quiescent. For example,
8 out of the 10 cores produced at the middle point of our standard
simulation have subsonic internal motions. The cores tend to be moderately
supercritical, and thus remain magnetically supported to a large extent.
They contain a small fraction of the cloud mass, and have lifetimes
ranging from $\sim 1.5 - 10$ times their local gravitational collapse
time. Some of the cores collapse to form stars, while others disperse
away without star formation, in agreement with previous work. All these
factors, as well as core-outflow interaction, contribute to the low
efficiency of the star formation in these clouds of dispersed star
formation.}
% Journal
{ Accepted by ApJ}
%% Preprints URL
astro-ph/0502130
\v5
{\large\bf{Large Confinement-Driven Spatial Variations in the Cosmic Ray Flux}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Paolo Padoan$^1$ \ and John Scalo$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Physics, University of California, San Diego,
CASS/UCSD 0424, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA} \\
$^2$ {Department of Astronomy, University of Texas, Austin, TX 78712, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: ppadoan@ucsd.edu; parrot@astro.as.utexas.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{The Galactic cosmic--ray (CR) flux is usually assumed to be relatively
constant on scales less than a few hundred parsecs, while estimates
of the CR ionization rate in diffuse ISM regions are larger than in
molecular regions by factors of 10-50. We show that the observed
CR variations can be understood in terms of self--confinement of
low--energy CRs by resonant pitch--angle scattering with self--generated
MHD waves in mostly neutral regions. The self--confinement yields a CR
density proportional to the square root of the local ion density,
and dropping sharply at densities above which damping of the waves
allows the CRs to stream freely.}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal \\
Preprint available at: http://xxx.lanl.gov/abs/astro-ph/0503585 }
\v5
%%--------SubmissionID=99----------------
%% Title
{\large\bf{Theoretical HDO emission from low-mass protostellar envelopes}}
%% Authors
{\bf{ B\'ereng\`ere Parise$^{1}$, Cecilia Ceccarelli$^{2}$ and S\'ebastien Maret$^{3}$}}
%% Institutions
$^1$ {Max-Planck Institut f\"ur Radioastronomie, Auf dem H\"ugel 69, 53121 Bonn, Germany} \\
$^2$ {Laboratoire d'Astrophysique, Observatoire de Grenoble - BP 53, F-38041 Grenoble cedex 09, France} \\
$^3$ {Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor MI 48109-1042, USA}
%% Email
{E-mail contact: bparise@mpifr-bonn.mpg.de}
%% LATEX COMMANDS
%% Abstract body
{We present theoretical predictions of the rotational line emission of
deuterated water in low-mass protostar collapsing envelopes. The
model accounts for the density and temperature structure of the
envelope, according the inside-out collapse framework. The deuterated
water abundance profile is approximated by a step function, with a low
value in the cold outer envelope and a higher value in the inner
envelope where the grain mantles evaporate. The two abundances are
the two main parameters of the modeling, along with the temperature at
which the mantles evaporate. We report line flux predictions for a 30
and 5 L$_\odot$ source luminosity respectively. We show that ground
based observations are capable to constrain the three parameters of
the model in the case of bright low-mass protostars (L$>$10
L$_{\odot}$), and that no space based observations, like for example
HSO observations, are required in this case. On the contrary, we show
that the study of low-luminosity sources (L$